Even though the automotive industry has over the years, if for no other reason than seeking competitive advantages, continually exerted efforts to increase the fuel economy of automotive engines, the gains continually realized thereby have been deemed by various levels of government as being insufficient. Further, such levels of government have also arbitrarily imposed regulations specifying the maximum permissible amounts of carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NO.sub.x) which may be emitted by the engine exhaust gas into the atmosphere.
Unfortunately, generally, the available technology employable in attempting to attain increases in engine fuel economy is contrary to that technology employable in attempting to meet the governmentally imposed standards on exhaust emissions.
For example, the prior art in attempting to meet the standards for NO.sub.x emissions has employed a system of exhaust gas recirculation whereby at least a portion of the exhaust gas is re-introduced into the cylinder combustion chamber to thereby lower the combustion temperature therein and consequently reduce the formation of NO.sub.x.
The prior art has also proposed the use of engine crankcase recirculation means whereby the vapors which might otherwise become vented to the atmosphere are introduced into the engine combustion chambers for further burning.
The prior art has also proposed the use of fuel metering means which are effective for metering a relatively overly rich (in terms of fuel) fuel-air mixture to the engine combustion chamber means as to thereby reduce the creation of NO.sub.x within the combustion chamber. The use of such overly rich fuel-air mixtures results in a substantial increase in CO and HC in the engine exhaust which, in turn, requires the supplying of additional oxygen, as by an associated air pump, to such engine exhaust in order to complete the oxidation of the CO and HC prior to its delivery into the atmosphere.
The prior art has also heretofore proposed employing the retarding of the engine ignition timing as a further means for reducing the creation of NO.sub.x. Also, lower engine compression ratios have been employed in order to lower the resulting combustion temperature within the engine combustion chamber and thereby reduce the creation of NO.sub.x. In this connection the prior art has employed what is generally known as a dual bed catalyst. That is, a chemically reducing first catalyst is situated in the stream of exhaust gases at a location generally nearer the engine while a chemically oxidizing second catalyst is situated in the stream of exhaust gases at a location generally further away from the engine and downstream of the first catalyst. The relatively high concentrations of CO resulting from the overly rich fuel-air mixture are used as the reducing agent for NO.sub.x in the first catalyst while extra air supplied (as by an associated pump) to the stream of exhaust gases, at a location generally between the two catalysts, serves as the oxidizing agent in the second catalyst. Such systems have been found to have various objections in that, for example, they are comparatively very costly requiring additional conduitry, air pump means and an extra catalyst bed. Further, in such systems, there is a tendency to form ammonia which, in turn, may or may not be reconverted to NO.sub.x in the oxidizing catalyst bed.
The prior art has also proposed the use of fuel metering injection means for eliminating the usually employed carbureting apparatus and, under superatmospheric pressure, injecting the fuel through individual nozzles directly into either the respective cylinders of a piston type internal combustion engine or into the engine intake manifold at an area in close proximity to the respective or associated engine cylinder intake valve. Since the quantity of fuel thusly metered and ultimately discharged by such nozzle, per cycle, is relatively very small, the nozzle pintle and associated orifice is also relatively very small. This, in turn, requires that the metered fuel be as clean and free of entrained foreign particles as possible prior to its discharge between the pintle and discharge orifice because even a very small particle of foreign matter could lodge between the pintle valve and associated discharge orifice resulting in preventing the subsequent closure of the discharge orifice by the pintle valve.
The prior art has employed a filter within each of such injector nozzle assemblies generally immediately upstream of the pintle valve and discharge orifice to thereby filter-out any fuel-entrained foreign particles before such have a chance to reach the pintle valve and discharge orifice.
One of the problems of such prior art injector nozzle assemblies is that the overall body or housing is made of one-piece metal and upon the internally disposed filter becoming clogged, the entire injector nozzle assembly has to be discarded and replaced by an entirely new injector nozzle assembly at a high cost factor. The same applies to those situations where any other internally disposed component or element should fail.
Accordingly, the invention as disclosed and described is directed, primarily, to the solution of such and other related and attendant problems of the prior art.